Conventionally, magnetic disk apparatuses have employed the CSS (Contact Start and Stop) system in which a magnetic head is held in contact with a contact-sliding inner region surface on a magnetic disk while the apparatus is stopped, then at the time of start-up, the magnetic head is slightly flown up while sliding in contact with the inner region surface and then recording/reproduction is started on a recording/reproducing region surface located outside the contact-sliding inner region surface. In this CSS system, it is necessary to provide the contact-sliding region on the magnetic disk apart from the recording/reproducing region.
Further, in the CSS system, in order to prevent contact adhesion between the magnetic disk and the magnetic head while being stopped, it is carried out to provide a concave-convex shape with a certain surface roughness, called texture, on the main surface of the magnetic disk. Further, in the CSS system, it is carried out that the surface of the magnetic disk is coated with a protective layer in order to protect the magnetic disk from contact sliding of the magnetic head, and so on.
On the other hand, in recent years, the LUL (Load Unload) system capable of an increase in recording capacity has started to be employed. In the LUL system, a magnetic head is retreated to an inclined platform called a ramp located outside a magnetic disk while being stopped, then at the time of start-up, the magnetic head is caused to slide from the ramp, after the magnetic disk starts to rotate, so as to fly over an LUL region on a surface of the magnetic disk to perform recording/reproduction and, therefore, the magnetic head does not make contact sliding on the magnetic disk.
In the LUL system, since it is not necessary to provide a contact-sliding region for the magnetic head on the surface of the magnetic disk as in the CSS system, there is an advantage in that a larger area of a recording/reproducing region can be ensured as compared with the CSS system and thus the recording capacity of the magnetic disk can be increased.
Further, in the LUL system, since the magnetic disk and the magnetic head are not brought into contact with each other, it is not necessary to provide texture as in the CSS system and thus the surface of the magnetic disk can be further smoothed. Consequently, there is also an advantage in that it is possible to reduce the flying height of the magnetic head (10 nm or less) as compared with the case of the CSS system and thus to increase the recording density of the magnetic disk.    Patent Document 1: JP-A-2004-127493